As the worldwide demand for natural gas grows, the need to develop remotely located sources of natural gas becomes increasingly more important. Often, however, the high cost of building the infrastructure necessary to deliver natural gas from such remote locations negates the financial incentives to develop these sources. Thus, there is a need to reduce the costs associated with constructing facilities such as pipelines to deliver natural gas to market.
In recent years, several major oil and gas companies have invested significant resources into developing high strength steels for use in large diameter natural gas pipelines, such as pipelines ranging from 36-inches to 54-inches in diameter. A shorthand terminology has been developed by American Petroleum Institute (API) Specification 5L to designate grades of line pipe steel using the letter “X” followed by a number corresponding to its minimum yield strength. For example, X100 steel has a minimum yield strength of 100,000 pounds per square inch (psi), and similarly, X120 steel has a minimum yield strength of 120,000 psi. Generally, grade X70 or lower is considered “conventional strength steel”, whereas grades above X70 are considered “high strength steel”, typically beginning at grade X80.
High strength steel has a relatively low crack resistance, so if a pipe were to become damaged and a crack were to form, that crack may propagate along the pipeline for many miles. To prevent these running cracks, crack arrestors may be placed at locations along the pipeline, for example, every two to four miles. A crack arrestor may comprise a welded steel ring or a bonded composite ring disposed around the outer surface of a pipe. Representative composite crack arrestors are manufactured and sold by Clock Spring Company, L.P. of Houston Tex. In addition, high strength steel manufacturing capacity is low, welding of high strength steel is complicated, and high strength steels have a lower plastic strain capacity than conventional steels, which may limit their use in applications requiring a high plastic strain capacity, such as pipelines installed in permafrost and seismic areas, for example.
Thus, to develop remotely located sources of natural gas, a need exists for an economical means to deliver such gas to market.